EpiTRENDS - Washington State Department of Health
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epiTRENDS A Monthly Bulletin on Epidemiology and Public Health Practice in Washington
June 2021 Volume 26, Number 6
Harmful Algal Blooms
Harmful algal blooms (HABs) occur in
both freshwater and marine systems.
Freshwater HABs, also known as Scott Lindquist, MD, MPH
cyanobacteria and their toxins, refers to State Epidemiologist,
aquatic phytoplankton/bacteria growth Communicable Disease
that may produce toxins harmful to Marcia J. Goldoft, MD
people, animals, or the environment. This Dolichospermum sp. responsible Scientific Editor
for a microcystins advisory in
issue will mainly focus on freshwater Pacific County, WA 2021 You may subscribe, update
HABs. subscription preferences or
unsubscribe to epiTRENDS
at Department of Health
Freshwater Harmful website.
Algal Blooms To obtain epiTRENDS in
an alternative format
Freshwater HABs are please contact:
primarily caused by
WA State Dept. of Health
cyanobacteria, formerly Communicable Disease Epi
known as “blue-green 1610 NE 150th Street
Shoreline, WA 98155
algae.” The growth of these 206-418-5500
aquatic organisms is
promoted by warm
temperatures, increased nutrients such as nitrogen and
phosphorus from residential or agricultural use of
fertilizers entering the water, low water flows during
droughts, and other environmental changes. A
cyanobacterial bloom may cause discoloration or scum
on water’s surface but can also occur without any
visible change to the water. In addition, not all visible
blooms have harmful effects. Therefore the only way to
know if an algal bloom is toxic is through testing the
Cyanopigment dispersal during toxic bloom water.
dissipation at Lake McDonald, WA. Photo: Sally Abella
King County Department of Natural Resources.
DOH 420-002
PAGE 2 epiTRENDS June 2021
HABs may produce cyanotoxins that
can negatively impact humans, pets, Freshwater and Marine Harmful Algal Blooms: Associated
livestock, wildlife, and other Algae, Toxins and Signs and Symptoms by Exposure
animals. Some dense blooms may Water Body Freshwater Marine
not produce toxins, while water that
Type of Cyanobacteria Microalgae (diatoms,
looks clear can have high levels of
aquatic algae dinoflagellates)
toxins. Cyanotoxins include
neurotoxins (e.g., anatoxins, Toxins Microcystins, Brevetoxins,
saxitoxins), hepatotoxins (e.g., produced anatoxins, azaspiracids,
microcystins, cylindrospermopsins), saxitoxins, ciguatoxins, domoic
and dermatotoxins. cylindrospermopsins acid, okadaic acid,
and others dinophysistoxins and
Exposures to cyanotoxins in others
recreational water or drinking water
can occur through: Skin contact Skin, eye, nose or Skin, eye, or throat
• Direct skin or eye contact or inhalation throat irritation; irritation; shortness of
respiratory illness breath, coughing,
when swimming or
sneezing
recreating in contaminated
water Ingestion Abdominal pain, Nausea, vomiting,
(swallowing headache, diarrhea, abdominal
• Swallowing contaminated water or neurologic pain, peripheral or
drinking water or eating symptoms, central nervous system
recreational water contaminated vomiting, diarrhea, symptoms (e.g.,
seafood) liver damage, paralytic, diarrhetic or
• Consuming contaminated kidney damage domoic acid shellfish
fish or shellfish poisoning)
• Inhaling toxins from aerosols or droplets from water
While freshwater exposures to HAB toxins are often associated with swimming or other outdoor
recreational activities, drinking water distribution systems that draw from contaminated bodies of
water can also be a source of exposure. In 2014, an algal bloom in Lake Erie resulted in unsafe
levels of microcystin in drinking water. In response, the city of Toledo, Ohio issued a water
advisory for over 400,000 people to use alternate water sources for drinking, cooking, and bathing.
Summit Lake in Thurston County, Washington, experienced an anatoxin-a bloom in 2017 that
closed the lake as a drinking water source for over 470 homes, and Salem, Oregon closed their
water system (serving 192,000 people) due to cyanotoxins in 2018.
illnesses Associated with Harmful Algal Blooms
A variety of illnesses in humans and animals have been associated with cyanotoxins. The nature
and severity of the illness depends on the route of exposure, the amount of toxin, the type of toxin,
and the length of time exposed. Symptoms usually begin within hours of exposure and can last for
a few days, although chronic exposure to liver toxins can present symptoms long after exposure
(e.g., a daily swimmer exposed to microcystins over months can develop liver issues over time).
Skin or eye exposure can cause rashes, swelling, sores, and visual disturbance. Inhaling
aerosolized water can result in nose and throat irritation, cough, chest tightness, wheezing, and
shortness of breath. Ingestion can cause abdominal pain, vomiting, diarrhea, and neurologic effects
(such as confusion and tingling sensations), and liver or kidney damage; severe cases from
PAGE 3 epiTRENDS June 2021
ingestion can result in death. Non-specific symptoms reported during outbreaks include headache,
dizziness, back pain, muscle aches, weakness, and fatigue
Identifying illnesses associated with HABs is typically a diagnosis of exclusion, based on
symptoms, reported exposures, and ruling out other possible causes. Liver function tests may be
useful when exposure to hepatotoxins (e.g., microcystins) may have occurred.
Illnesses have also been described in animals after exposure to algal toxins. With longer skin
exposures or higher levels of ingestion than a person would typically experience, animals have had
severe symptoms such as excessive salivation, weakness, staggered walking, difficulty breathing,
or convulsions. Death in animals has occurred within hours or days of exposure.
Surveillance: Citizens and health care providers (including
veterinarians) should report suspected human and animal LHJs should report all
HAB-associated illnesses to their local health jurisdiction. suspected human or animal
Local health jurisdictions should report all suspected human
or animal HABs-associated illnesses or deaths to the
HABs-associated illnesses
Department of Health (DOH) Office of Communicable or deaths to the DOH Office
Disease Epidemiology (206-418-5500). DOH can advise or of Communicable Disease
assist with illness investigations. DOH will facilitate
reporting of human and animal cases to the CDC via CDC’s Epidemiology at 206-418-
the One Health Harmful Algal Bloom System (OHHABS) 5500.
and reporting of human HABs-associated illness outbreaks
via the National Outbreak Reporting System (NORS).
Water monitoring. The Washington State Department of Ecology’s Freshwater Algae Monitoring
Program, in partnership with the King County
Environmental Laboratory, identifies algal
blooms, does toxicity testing for residents and
local health jurisdictions, and has a searchable
database showing testing results
(nwtoxicalgae.org). Five years of lake
monitoring show a seasonal pattern for
microcystin concentration, with the majority of
elevation sample result during late summer
and early fall. Not all lakes follow this pattern
– blooms can occur earlier in the summer and
others even in mid-winter. Climate change
may expand the number of lakes experiencing
HABs.
A decade ago, DOH collaborated with local health jurisdictions (LHJs) and other agencies to
develop a three-tier Lake Management Protocol for posting lakes with toxic algal blooms. DOH
received six-month of funding in January 2021 to update standards using EPA’s recreational
guidance, incorporate county input regarding a two-tiered versus the current three-tiered lake
management protocol, update signs with additional languages for posting at state waters, and
develop and communicate methods for reporting animal and human health illnesses to DOH by
lake managers/LHJs and by DOH to CDC’s (OHHABS) national database.
PAGE 4 epiTRENDS June 2021
In May 2021, a DOH survey to LHJs, tribal nations and other agencies
asked how to improve Washington’s HAB lake management approach.
Based on responses, two major updates have been incorporated:
• Addition of an informational sign for year-round posting at lakes
with a history of blooms
• Adoption of a two-tier protocol (WARNING and DANGER
signs).
In addition, the primary messages were translated into seven languages
identified by lake managers and validated using census data based on an
approach developed by King County. Languages were ranked by the
number of people and percentage of speakers for the east and west side of
the state, allowing informed use of one set of signs statewide. A statewide
webinar/workshop allowed discussion of survey responses and directed
future collaborations.
Prevention
Practices that help prevent algal growth in lakes include properly applying
fertilizers so that nutrients are not washed into fresh or marine waters,
picking up animal waste and encouraging natural vegetation along lake
shorelines.
People should protect themselves, their pets, and livestock from possible
exposure to contaminated water. Drinking directly from lakes and rivers
should be avoided even when the water looks clear. In addition, people
and their animals should avoid going into or playing in a body of water
that:
• Has foam, scum, or algal mats on the surface
• Smells bad
• Looks discolored
• Contains or is near dead fish or other dead animals (e.g., lake with dead fish on its shore)
If a water advisory is issued, the water should not be used for any purpose. Boiling the water does
not inactivate the toxins, and skin exposure should be avoided. It is important to provide
alternative sources of safe drinking water, particularly for children, pets and livestock.
If people think that they or their animals had recent exposure to water contaminated with a
harmful algal bloom, they should rinse their bodies with clean, fresh water as soon as possible.
People or owners of pets exhibiting signs or symptoms of a HAB-associated illness should consult
with a health care provider or veterinarian and mention the recent exposure.
Although reported illnesses from harmful algal blooms are currently rare in Washington State,
several animal deaths have been reported over the years. Toxic blooms can occur in any month of
the year, with most high toxin concentrations observed during August and September, and climate
change could increase this problem in future years. People or their animals who engage in
recreational activities in these waters could be at risk. Simple precautions can prevent exposure to
water contaminated with HABs.
PAGE 5 epiTRENDS June 2021 Resources DOH overview: doh.wa.gov/CommunityandEnvironment/Contaminants/BlueGreenAlgae DOH water system guide: doh.wa.gov/CommunityandEnvironment/Contaminants/BlueGreenAlgae/Resources DOH Cyanobacteria Resources: https://www.doh.wa.gov/CommunityandEnvironment/Contaminants/BlueGreenAlgae/Resources Washington State Department of Ecology: ecology.wa.gov/Research-Data/Monitoring-assessment/Puget-Sound-and-marine- monitoring/Marine-algae-plankton Washington State Toxic Algae (Freshwater algae bloom monitoring program): nwtoxicalgae.org CDC overview: cdc.gov/habs Reporting (One Health Harmful Algal Bloom System-OHHABS): cdc.gov/habs/ohhabs CDC prevention and control: cdc.gov/habs/prevention-control
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